Abstract
Objectives
This study was designed to evaluate the effect of sandblasting and metal primers on the shear bond strength of three commercial resin cements to Yttria-Tetragonl Zirconia Polycrystal (Y-TZP) ceramics.
Methods
One hundred and twenty Y-TZP ceramic cylinders (Ø7 mm × 12 mm) were embedded in polytetrafluoroethylene (PTFE) molds using PMMA. The specimens were divided randomly into 12 groups ( n = 10), according to the surface treatments (control; sandblast-only; metal primer-only; sandblast + metal primer) and metal primer-resin cements (Alloy primer – Panavia F 2.0, V-primer – Superbond C&B, Metaltite – M bond) rendered. The mixed resin cements were placed onto the treated zirconia surfaces in cylindrical shape (Ø3 mm × 3 mm) using PTFE molds. All specimens were thermocycled (5 and 55 °C, 5000 cycles) and subjected to shear bond strength test by a universal testing machine with a crosshead speed of 0.5 mm/min. All data were statistically analyzed using two-way ANOVA and multiple comparison Scheffé test ( α = 0.05), and SEM images of the fractured areas were used to evaluate the fracture mode.
Results
In Panavia F 2.0, the bond strength of the specimens treated with sandblasting and metal primer (Alloy primer) was significantly higher than those of the other subgroups. In Superbond C&B and M bond, sandblasting significantly increased the shear bond strength, but the effect of metal primers (V-primer and Metaltite) was not significant and there was disordinal interaction.
Significance
Metal primers are not always effective for bonding between Y-TZP ceramics and resin cements. Even though a metal primer is not enough to be used alone, combined application with sandblasting seems to be an appropriate pretreatment for improving the bond strength of resin cement to Y-TZP ceramics, especially in Panavia F 2.0.
1
Introduction
In recent years, the demand for metal-free fixed dental prosthesis (FDP) with more esthetic and biocompatibility has increased. As a result, various all-ceramic materials with optimized mechanical properties have been developed . Yttria-Tetragonl Zirconia Polycrystal (Y-TZP) ceramic is one of the most commonly used all-ceramic core materials today because of its highest fracture toughness and chemical durability .
Glass structure in ceramics reacts with moisture from saliva. This causes the subcritical crack propagation and stress corrosion, leading to decomposition of the glass structure and impairment of long-term stability of the ceramics . However, zirconia cores are composed of glass-free, polycrystalline microstructure, and consequently show off outstanding long-term stability . One of the problems is the inferior adhesion capability of resin cements to such ceramics . This is related to glass-free composition structure, characterizing zirconia as acid-resistant material . For this reason, there have been considerable efforts by many manufacturers and researchers to modify the surface properties of zirconia, mechanically and chemically by various surface treatments .
Several techniques, especially the airborne particle abrasion with alumina, have been reported to facilitate “mechanically” the bond strength between resin cement and Y-TZP ceramic . In addition, tribochemical silica coating in dental laboratories was suggested as an effective method for bonding , but recently, it has also been criticized for possibility of subcritical crack propagation within zirconia .
On the other hand, various adhesive monomers, metal primers, have been developed to achieve “chemically” improved adhesion between resin cement and base or noble metals . Initially, such metal primers were indicated for the repair of fractured metal–ceramic FDPs with metal exposure . The adhesive functional metal primers bond powerfully to pure metals and alloys, because of their affinity to metal oxides that exist on the metal surface . The zirconium surface is easily covered with a passive oxide film (ZrO 2 ), similar to the titanium surface (TiO 2 ) . Thus, chemical characteristics of zirconia ceramic surface are similar to those of metal surface. Although it is possible to use a metal primer to increase bond strength between zirconia surface and resin cement, available information regarding its effect on the bond strength is limited. Hence, the objective of this study was to evaluate the effect of sandblasting and various metal primers on the bond strength between resin cements and Y-TZP ceramics. The null hypothesis to be tested was that there was no significant effect of metal primers on the shear bond strength between resin cements and Y-TZP ceramics.
2
Materials and methods
2.1
Preparation of the specimens
Cylindrical (7 mm in diameter, 12 mm in height) Y-TZP ceramics – which consisted of 88–96% ZrO 2 , 4-6% Y 2 O 3 and <1% Al 2 O 3 – (Rainbow, Dentium, Seoul, Korea) were embedded in polytetrafluoroethylene (PTFE) molds (10 mm in inner diameter, 20 mm in outer diameter, 12 mm in height) using polymethylmethacrylate resin (Vertex-Dental, Dentimex, Zeist, Netherlands), ensuring that one surface of the zirconia cylinder remained uncovered for adhering to resin cement. The exposed surface of each specimen was polished, ground with 1200-grit silicone carbide abrasive under water cooling, and ultrasonically cleaned in distilled water for 5 min.
2.2
Surface conditioning and bonding procedure
The 120 specimens were randomly divided into 12 groups depending upon the type of the surface treatments and resin cement to be applied ( N = 120, n = 10/group). The abbreviations of the experimental groups, surface conditioning methods and resin cements used are presented in Table 1 .
| Code | Sandblasting | Metal primer | Resin cement |
|---|---|---|---|
| NNP | No | No | Panavia F 2.0 |
| SNP | Yes | No | Panavia F 2.0 |
| NPP | No | Alloy primer | Panavia F 2.0 |
| SPP | Yes | Alloy primer | Panavia F 2.0 |
| NNS | No | No | Superbond C&B |
| SNS | Yes | No | Superbond C&B |
| NPS | No | V-primer | Superbond C&B |
| SPS | Yes | V-primer | Superbond C&B |
| NNM | No | No | M bond |
| SNM | Yes | No | M bond |
| NPM | No | Metaltite | M bond |
| SPM | Yes | Metaltite | M bond |
Three commercial resin cements were chosen: a dual-cured resin cement (Panavia F 2.0, Kuraray Medical Co. Ltd., Osaka, Japan), chemically polymerized resin cement (Superbond C&B, Sun Medical Co. Ltd., Moriyama, Japan), and self-etching adhesive resin cement (M bond, Tokuyama Dental Corp., Tokyo, Japan) ( Table 2 ). Three kinds of metal primers were used, which were produced and recommended by the same manufacturers for each resin cement ( Table 2 ).
| Brand name | Batch number | Composition | Manufacturer |
|---|---|---|---|
| Alloy primer | 249AB | VBATDT and MDP in acetone | Kuraray Medical Co., Osaka, Japan |
| V-primer | MR1 | 0.5% VBATDT in acetone | Sun Medical Co., Kyoto, Japan |
| Metaltite | 02296 | MTU-6 in ethanol | Tokuyama Dental Corp., Tokyo, Japan |
| Panavia F 2.0 | 51181 | MDP | Kuraray Medical Co., Osaka, Japan |
| Paste A: BPEDMA, MDP, DMA | |||
| Paste B: Al-Ba-B-Si glass, silica containing composite | |||
| Superbond C&B | RE1 | Powder: PMMA | Sun Medical Co., Kyoto, Japan |
| Liquid: MMA, 4-META | |||
| Catalyst: TBB | |||
| M bond | X764847 | Powder: PMMA, BPO | Tokuyama Dental Corp., Tokyo, Japan |
| X7658Y7 | Liquid: MMA, MAC-10, amine | ||
Airborne particle abrasion on the specimen using 90 μm grain sized Al 2 O 3 particles was performed making circular movements at a standoff distance of 10 mm with 3.8 bar pressure for 15 s. The substrate surface was rinsed for 20 s and air-dried for 5 s. Metal primer was coated on the surface in a layer as thinly as possible with a disposable brush.
A PTFE ring with an opening (3 mm in inner diameter and 3 mm in depth) was then positioned on the treated side of the specimen. The resin cements were mixed according to manufacturers’ instructions, packed into the PTFE ring incrementally using a hand instrument and cured by the same operator. The specimens were left to polymerize for 30 min at 23 ± 1 °C. After setting, the PTFE mold was gently removed from the specimen.
All specimens were stored in distilled water for 24 h at 37 °C and then subjected to thermocycling for 5000 cycles between 5 and 55 °C. The dwelling time at each temperature was 30 s, and the transfer time from one bath to another was 2 s.
2.3
Shear bond strength test
The specimens were mounted in the jig of a universal testing machine (Model 3345, Instron, Canton, MA, USA), and load was applied to the adhesive interface at a constant crosshead speed of 0.5 mm/min until failure occurred. The maximum force (MPa) to produce fracture was recorded using a corresponding software.
2.4
Statistical analysis
Statistical analysis was performed using SAS 9.1.3. (Enterprise, SAS Institute Inc., NC, USA). The mean values of each group were statistically analyzed using two-way ANOVA and the multiple comparison Scheffé test, with shear bond strength as the dependent variable, and the two types of surface treatments (sandblasting and metal primer) as the respective independent factors. p values less than 0.05 were considered to be statistically significant in all tests.
2.5
Scanning electron microscope (SEM) examination
A scanning electron microscope (SEM; VEGA II LSH, TESCAN, Brno, Czech Republic) at 180× and 2000× magnification and 10 kV accelerating voltage was used to investigate the fractured surface and the resin bonding on zirconia. Typical cases were used for illustration.
2
Materials and methods
2.1
Preparation of the specimens
Cylindrical (7 mm in diameter, 12 mm in height) Y-TZP ceramics – which consisted of 88–96% ZrO 2 , 4-6% Y 2 O 3 and <1% Al 2 O 3 – (Rainbow, Dentium, Seoul, Korea) were embedded in polytetrafluoroethylene (PTFE) molds (10 mm in inner diameter, 20 mm in outer diameter, 12 mm in height) using polymethylmethacrylate resin (Vertex-Dental, Dentimex, Zeist, Netherlands), ensuring that one surface of the zirconia cylinder remained uncovered for adhering to resin cement. The exposed surface of each specimen was polished, ground with 1200-grit silicone carbide abrasive under water cooling, and ultrasonically cleaned in distilled water for 5 min.
2.2
Surface conditioning and bonding procedure
The 120 specimens were randomly divided into 12 groups depending upon the type of the surface treatments and resin cement to be applied ( N = 120, n = 10/group). The abbreviations of the experimental groups, surface conditioning methods and resin cements used are presented in Table 1 .
| Code | Sandblasting | Metal primer | Resin cement |
|---|---|---|---|
| NNP | No | No | Panavia F 2.0 |
| SNP | Yes | No | Panavia F 2.0 |
| NPP | No | Alloy primer | Panavia F 2.0 |
| SPP | Yes | Alloy primer | Panavia F 2.0 |
| NNS | No | No | Superbond C&B |
| SNS | Yes | No | Superbond C&B |
| NPS | No | V-primer | Superbond C&B |
| SPS | Yes | V-primer | Superbond C&B |
| NNM | No | No | M bond |
| SNM | Yes | No | M bond |
| NPM | No | Metaltite | M bond |
| SPM | Yes | Metaltite | M bond |
Three commercial resin cements were chosen: a dual-cured resin cement (Panavia F 2.0, Kuraray Medical Co. Ltd., Osaka, Japan), chemically polymerized resin cement (Superbond C&B, Sun Medical Co. Ltd., Moriyama, Japan), and self-etching adhesive resin cement (M bond, Tokuyama Dental Corp., Tokyo, Japan) ( Table 2 ). Three kinds of metal primers were used, which were produced and recommended by the same manufacturers for each resin cement ( Table 2 ).
| Brand name | Batch number | Composition | Manufacturer |
|---|---|---|---|
| Alloy primer | 249AB | VBATDT and MDP in acetone | Kuraray Medical Co., Osaka, Japan |
| V-primer | MR1 | 0.5% VBATDT in acetone | Sun Medical Co., Kyoto, Japan |
| Metaltite | 02296 | MTU-6 in ethanol | Tokuyama Dental Corp., Tokyo, Japan |
| Panavia F 2.0 | 51181 | MDP | Kuraray Medical Co., Osaka, Japan |
| Paste A: BPEDMA, MDP, DMA | |||
| Paste B: Al-Ba-B-Si glass, silica containing composite | |||
| Superbond C&B | RE1 | Powder: PMMA | Sun Medical Co., Kyoto, Japan |
| Liquid: MMA, 4-META | |||
| Catalyst: TBB | |||
| M bond | X764847 | Powder: PMMA, BPO | Tokuyama Dental Corp., Tokyo, Japan |
| X7658Y7 | Liquid: MMA, MAC-10, amine | ||
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